The invention relates to a wireless communication system and a radio base station apparatus and a network control apparatus constructing the wireless communication system.
In cellular wireless communication, an examination and a practical implementation of multicast services for broadcasting same information to a plurality of terminals are being progressed. Generally, a transmission of the multicast services is performed in the downlink, which is the direction from a base station to the terminal. Unlike a unicast system in which a dedicated radio resource is allocated to one terminal, in the multicast system, since a plurality of terminals share the same radio resource, use efficiency of the radio resource is improved. Further, by transmitting the same information from a plurality of base stations, the terminal uses the received signals from a plurality of base stations and can improve quality of the received signals.
In the multicast system using a plurality of base stations, an SFN (Single Frequency Network) by an OFDM (Orthogonal Frequency Division Multiplexing) signal has been examined. In the OFDM-SFN system, a plurality of base stations transmit a same radio signal by using a same frequency. The terminal does not need to separate the radio signal from each base station and it is sufficient to receive and demodulate a signal in which the radio signals from a plurality of base stations have been superposed.
In the standardization organization 3GPP, in an E-UTRA (Evolved Universal Terrestrial Radio Access) and an E-UTRAN (Evolved Universal Terrestrial Radio Access Network), a multicast system using the OFDM has been standardized. In “3GPP TS 36.300 V9.1.0, 15 MBMS”, it has been disclosed as MBMS (Multimedia Broadcast and Multicast Services).
In the cellular wireless communication, a small base station has been examined in order to complement an area coverage. It is presumed that the small base station is disposed, particularly, in a home, an office, a commercial building, or the like and is connected to a dedicated network of a mobile network operator through an ISP (Internet Service Provider) line or the like. In such a small base station, since a cover area (cell) of a radio wave is narrower than that of the ordinary base station, the cover area of the ordinary base station is called a “macrocell”, while the cover area of the foregoing small base station is called a “femto-cell”.
In the standardization organization 3GPP, in the E-UTRA and the E-UTRAN, the femto-cell base station has been standardized. In “3GPP TS 36.300 V9.1.0, 4.6 Support of HeNBs”, a femto-cell base station has been disclosed as an HeNB (Home E-UTRAN Node B).
In JP-A-2009-182944, in the E-UTRA and the E-UTRAN, an environment where a base station which executes only the unicast transmission, a base station which executes only the MBMS transmission, and a base station which executes both of the unicast transmission and the MBMS transmission exist mixedly has been disclosed.